(1) Field of the Invention
The present invention relates to photolithographic techniques in semiconductor manufacturing and, more particularly, to anti-reflection coating for metal photolithography.
(2) Description of the Prior Art
In the construction of semiconductor integrated circuits, a photoresist layer covering the metal layer is selectively exposed to actinic light through a photomask resulting in the pattern on the photoresist layer. The exposed metal layer is etched away to the underlying dielectric layer.
The high reflectivity of the metal layer could scatter the light so that the photoresist under the masked areas would be exposed resulting in an incorrect patterning of the metal layer. It is a known practice in the prior art to use an anti-reflection layer between the metal and the photoresist layers. U.S. Pat. No. 4,820,611 to Arnold, III et al describes the use of a titanium nitride anti-reflection layer over titanium or aluminum. U.S. Pat. No. 5,066,615 to Brady et al describes the use of a metal-silicon-nitride anti-reflection layer where the metal in said layer is titanium, chromium, or the like.